It is desirable to crosslink fluorinated, non-elastomeric thermoplastic polymers to improve their dimensional stability (creep resistance) in molded article form. The crosslinking of elastomeric fluorinated polymers with a variety of crosslinking agents to improve their elastic recovery and tensile modulus is well known (see, for example, U.S. Pat. No. 3,243,411 to Tawney et al). A known crosslinking agent for this purpose is the dipotassium salt of bis-phenol AF (commonly called K.sub.2 AF) This salt has the formula ##STR1## K.sub.2 AF is used in the aforementioned Tawney patent.
Heretofore, substantially perfluorinated fluorocarbon polymers that are non-elastomeric have not been crosslinked because they lack chemically reactive cure sites and are relatively inert chemically. It would be desirable to find a means to crosslink such copolymers to improve their dimensional stability (creep resistance) in molded form, even at the sacrifice of tensile strength.